Process of making polyolefin fibers

ABSTRACT

An improved process of manufacturing fibers by the technique of forming a mixture of polymer, solvent for such polymer and, optionally, water or other flashing aids, at a temperature (flash temperature) which is high enough to bring the polymer to a plastic state and which will permit substantially complete vaporization of the solvent when the mixture is flashed, flashing the mixture into a flash zone to produce a fibrous product and subsequently refining the fibrous product characterized in that the fibrous product is first cooled prior to passing it through a primary refining zone. The primary refining is effected under conditions that impart a vigorous fibrillating action to the fibrous product and provides a pulp having a drainage factor in excess of 1.0 seconds/gram.

United States tent 1 Suzuki et al.

[ 1 3,907,633 1 Sept. 23, 1975 7 Filed:

DISPERSING CELLULOSE XANTI-IATE FIBERS IN AN ACIDIC AQUEOUS MEDIUM CONTAINING A CAT IONIZED ALKYL BETAINE SURFACTANT Inventors: Migaku Suzuki, Ohtaltc: Atushi Kawai, Hiroshima, both of Japan Assignee: Mitsubishi Rayon (30., Ltd, Tokyo,

Japan June 13, 1974 Appl. No.: 479,038

Foreign Application Priority Data June 18, 1973 Japan 48/68505 US. Cl 162/157 C, 162/158, 162/183,

252/357, 246/194 Int. Cl. D2111 3/12 Field of Search 162/157 C, 158, 183;

References Cited UNITED STATES PATENTS 2/1973 Kawai et a1 162/157 C 3,320,117 5/1967 Aoki et a1 162/157 C 2,702,279 2/1955 Funderburk et a1 252/546 3,832,281 8/1974 Kawai 01 a1. (1) 162/157 C FOREIGN PATENTS OR APPLICATIONS OTHER PUBLICATIONS Schwartz et a1., Surface Active Agents & Detergents, Vol.11, 1958,13. 138. (GP 170) Japan Primary Examiner-S. Leon Bashore Assistant Examiner-Arthur L. Corbin Attorney, Agent, or Firm-Norman F. Oblon, et a1.

[57] ABSTRACT 4 Claims, No Drawing Figures US Patent Sept. 23,1975

NITROGEN FIBROUS SLURRV DISPERSING CELLULOSE XANTI-IATE FIBERS INAN ACIDIC AQUEOUS MEDIUM CONTAINING A CATIONIZED ALKYL BETAINE SURFACTANT BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention relates to a method for producing non-woven fabrics or paper-like materials having excellent properties by a wet method from fibers of unregenerated cellulose xanthate or hydroxymethyl cellulose xanthate.

DESCRIPTION OF THE PRIOR ART Unregenerated cellulose xanthate and hydroxymethyl cellulose xanthate are methylolation products of cellulose xanthate. Their fibers are strongly acidic and stable, but are characterized by quite high chemical reactivity. Fibers comprising unregenerated cellulose xanthate and a method for producing nonwoven fabrics or paper-like materials from the fibers are disclosed in U.S. Patent 3,320,117 and fibers comprising hydroxymethyl cellulose and a method for producing non-woven fabrics or paper-like materials from the fibers are disclosed in US. Patent 3,718,537 and U.S. Patent application Serial No. 267,994, filed June 30, 1972 (corresponding tov Italian Patent 962,732). g

These types of fibers have not heretofore been entirely successfully used in a wet process preparation of non-woven fabrics or paper-like materials, and it is now believed that the prior failures are attributable to an inability to properly disperse or distribute the fibers into the water. The use of dispersing accelerators has been considered, but heretofore, the high reactivity of the fibers have hindered effective use of such agents. It has now been discovered that a suitable such agent must have the properties of being:

1. acidic 2. highly water soluble (3H3 (3H3 012F125 CCH COONa 1-1 1:1 011 000 9 N at CH CH3 C'IHZCHZOH CHZCHZOH C H if CZCH COONa (1 13 --1;l (M 000 NaClZ 3. essentially chemically nonreactive with the fibers and cause no denaturation of the fibers 4. highly stable with respect to polyethylene oxide The objects of this invention are provided by the use of betaine surface active agents to impart good self-dispersibility to the unregenerated cellulose xanthate fibers. The betaine agent is used in an acidified condition. t 1

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, fibers which .can be used in preparing non-woven fabrics or paper like materials, comprising unregenerated cellulose xanthate, or hydroxymethyl cellulose xanthate, are provided. The fibers are treated with a betaine surface active agent, and particularly those having the chemical structure of alkyldimethylbetaine or alkyldihydroxyethylbetaine. These betaines have the structure T GnH lil CHQOO (IIH CH OH '.CnH CH' COO G) (b) CH CH OH wherein n is an integer of 12-18. Especially suitable CH CH These betaine surfactants have relatively good water-solubility and stability in acidic,neutral and alkaline media andare especially stable in acidic and alkaline media.

In order to increase the affinity of these surfactants for fibers in the acidic media used in the present invention,the surfactant is advantageously cationized by acidification with acetic acid, lactic acid, or the like, whereby the adsorbability of the surface active agents on the fibers will be increased and an extremely good dispersion effect will be obtained.

As mentioned above, the starting fibers used in the present invention are incompletely regenerated viscosefibers as used, for example, in U.S. Patent No. 3,320,117 of those comprising a derivative of cellulose xanthate, such as hydroxymethyl cellulose xanthate as'used, for example, in U.S. Patent No. 3,718,537 and U.S. Serial No. 267,994. These fibers are usually cut into lengths of about 440 mm while wet and are used for the conventional paper-making as disclosed in said patents.

A method for using the surfactant of the present invention will now be explained. The starting fibers may be dipped into a liquid containing the above surfactant under acidic conditions or said liquid may be sprayed or applied onto the fibers under acidic conditions at the spinning step or at any of the stretching and the subsequent steps. By subjecting the fibers to these treatments, spontaneous dispersi bility is imparted to the fibers and the thus treated fibers can then be dispersed into an acidic aqueous solution and used in a wet process technique for the formation of a paper-like product.

The starting fibers may also be directly dispersed into an acidic aqueous solution which contains the surfactant, andthe dispersion may be subjected to paper-making.

It becomes possible, by using said surfactant, to

homogeneously disperse the starting fibers and to produce homogeneous and excellent quality nonwoven fabric or paper-like material on an industrial scale.

The preferred concentration of the aqueous solution of the surfactant used for dispersion is -100 ppm, although higher concentrations may also be employed, if desired.

The preferred amount of the surfactant to be used is 0.05 to 1.5% based on the weight of the fibers.

1n the present invention, known dispersion stabiliz-' ing agents may, of course, be used in the dispersion EXAMPLE 1 A aqueous solution of lactic acid-acidified stearyldimethylbetaine (Product A) was diluted with hot water containing 1% acetic acid at 80C to prepare a 4% aqueous solution having a pH of 3.0.

A viscose containing 7.5% cellulose and 4% alkali and having a 7 value of 55 was prepared in the usual manner. This viscose was extruded into a coagulation bath containing 25 g/l of sulfuric acid, 0.5 g/l of zinc sulfate and 40 g/l of sodium sulfate at 23C. The resultant filamenttow was stretched by 150% in a bath containing 2 g/l of sulfuric acid, and 300 ppm (0.3% based on the weight of fibers) of product A at 20C and was cut'into lengths of 15 mm.

The resultant cut filament tow were dispersed in 7 an aqueous solution containing 20 ppm of product A step and the generally employed conditions for dispersion and paper-making may be used without any difficulty.

Paper-making processes from the fibers of the present invention are explained in detail in U.S.

Patent 3,320,117, U.S. Patent 3,718,537 and U.S. Serial No. 267,994.

In U.S. Serial No. 267,994, now U.S. Patent 3,832,281, non-woven fabrics or paper-like materials I are produced by (a) dispersing spun and stretched viscose fibers comprising hydroxymethyl cellulose xanthate in an aqueous medium having a pH of lower than 6.0 at a temperature of lower than 30C,

(b) forming the dispersed fibers into a web by a wet forming method,

c) dehydrating the web to the extent that the water content of the web becomes lower than 700%, said fibers after dehydration being characterized by:

(1) a hydroxymethyl cellulose xanthate content in terms of y-value of greater than 30,

(2) a decomposition degree of less than 75%, and

(3) a process swelling degree of lower than 250%,

(d) subjecting at least a portion of the surface of dehydrated web to a pressure of greater than 2 Kg/cm and having a pH of 5.0 to obtain an extremely homogeneous dispersion. This dispersion was subjected to paper-making by employing a cylindrical paper machine to obtain a uniform sheet. The thus obtained sheet was allowed to pass through an embossing roll having projections and having a surface temperature of 150C to effect partial fusion bonding. The thus treated sheet was then subjected to scouring treatments, such as hotacid treatment at C,'water washing, bleaching or the like, and dried.

For comparison, a filament tow which was not treated with product A was dispersed in a bath containing no product A and having a pH of 5.0 to cause dispersion of fibers. Many undispersed cut filament tow were present after dispersion. Dispersibility of this Example and the Comparative Example are compared in Table 1.

' TAB LE 1 Number of undispersed fibers I400 cm*) L M S Total The present Example 0 1 14 15 Comparative Example 3 8 20 31 Method of measurement of number of undispersed fibers:

A square 20 cmX 20 cm was drawn on the dried sheet as the area to be measured and this sample was placed on a measuring stand with a fluorescent lamp. Undispersed fibers within said area of 400 cm were marked with red magic ink and the number of undispersed fibers was counted with a counter. This measurement was effected two times andthe mean value was taken as the number of undispersed fibers within said area. In Tables 1 and 2, L M and S have the following meanings.

L: Undispersed fibers larger than 1.0 mm in width M: Undispersed fibers 0.5-1.0 mm in width S: Undispersed fibers less than 0.5 mm in width.

EXAMPLE 2 A 50% aqueous solution of lactic acid-acidified stearyldihydroxyethylbetaine (Product B) containing sodium chloride was diluted with hot water containing 1% acetic acid at 80C to prepare a 5% aqueous solution having a pH of 3.0.

A viscose containing 7% cellulose and 4.2% alkali and having a y value of 80 was prepared in accordance with the conventional method. This viscose was extruded into a coagulation bath containing 35 g/l of sulfuric acid, 8 g/l of formaldehyde and 80 g/l of sodium sulfate at 26C. The thus obtained filaments were stretched by 150% in a second bath containing 10 g/l of sulfuric acid at 60C to obtain -a filament fiber tow. This tow was continuously cut to lengths of mm and at the same time, the thus cut fibers were continuously introduced and dispersed in an aqueous solution containing 70 ppm (0.15% based on the weight of fibers) of product B and having a pH of 3.5 to obtain an extremely homogeneous dispersion. This dispersion was immediately subjected to papermaking by employing a cylindrical paper machine to obtain a sheet of homogeneous texture. The thus obtained sheet was passed through an embossing roll having a surface temperature of 130Cto cause partial fusion bonding and then was subjected to scouring treatments, such as hot acid treatment at 80C,

1 water washing, bleaching, or the like, and dried.

TABLE 2 The number of undispersed fibers [400 cm L M S Total The present Example 9 4 18 3] Comparative Example 10 21 46 77 Having now fully described the invention, it will be apparent to one of ordinary skill in the art that many changes and modifications can be made thereto without departing from the spirit or scope of the invention as set forth herein.

What is claimed is:

1. In a method for producing a non-woven fabric or a paper-like material by cutting fibers comprising unregenerated cellulose xanthate or cellulose xanthate derivative, dispersing the cut fibers in an acidic aqueous medium and then forming the dispersed fibers into a sheet, the improvement which comprises: treating said fibers under acidic conditions with a surfactant having the following structure:

wherein n is aninteger of 12-18, which surfactant is cationized by acidification, so as to impart good selfdispersibility to said fibers.

2. The method of Claim 1, wherein the treatment of the fibers with the cationized surfactant is carried out by dipping the fibers into a solution containing said cationized surfactant or by spraying or applying the solution to the fibers.

3. The method of Claim 1, wherein said surfactant is used in an amount of 0.05 to 1.5% based on the weight of fibers.

4. The method of Claim 1, wherein the concentration of the cationized surfactant in the aqueous solution is 10100 ppm.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 633 Dat d September 23 a 1975 Migaku Suzuki et a1. Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Cancel the sheet of drawing containing Figs. 1 and 2.,

Signed and Ska-led this Sixteenth D y 0f November 1976 [SEAL] Arrest.

RUTH C. M ASON C. MARSHALL DANN Alresling ()jjicer Commissioner nflamms and Trademarks 

1. IN A METHOD FOR PRODUCING A NON-WOVEN FABRIC OR A PAPER-LIKE MATERIAL BY CUTTING FIBERS COMPRISING UNREGENERATED CELLULOSE XANTHATE OR CELLULOSE XANTHATE DERIVATIVE DISPERSING THE CUT FIBERS IN AN ACIDIC AQUEOUS MEDIUM AND THEN FORMING THE DISPERSED FIBERS INTO A SHEET, THE IMPROVEMENT WHICH COMPRISES: TREATING SAID FIBERS UNDER ACIDIC CONDITIONS WITH A SURFACTANT HAVING THE FOLLOWING STRUCTURE:
 2. The process of claim 1 wherein the fibrous product is diluted with water to a consistency between about 1% and 10% by weight prior to refining.
 3. The process of claim 1 wherein refining is carried out by passing the fibrous material through a disc refiner with the spacing between the discs set at between about 0 and 2500 microns.
 4. The process of claim 3 wherein the discs are rotated at a relative velocity between about 4000 and 8000 feet/minute.
 5. The process of claim 1 wherein the fibrous product is subjected to a total power greater than about 0.2 kilowatt-hour/kilogram during refining.
 6. The process of claim 1 wherein the polymer is an at least partially crystalline polyolefin.
 7. The process of claim 1 wherein the polyolefin is polyethylene.
 8. The process of claim 1 wherein the primary refining is carried out under conditions to impart a vigorous fibrillating action to the fibrous product effective to produce a pulp having a drainage factor greater than 1.0 second/gram.
 9. The process of claim 1 wherein the primary refining is carried out under conditions to provide a pulp less than 90% by weight of which is retained on a 20 plus 35 mesh Tyler screens when passed therethrough at a consistency of 0.5% by weight. 